1. Field of the Invention
The present invention relates to a slide bush of a scroll compressor, and more particularly to an eccentric coupling device in a radial compliance scroll compressor, which is capable of sufficiently supplying oil, fed through an oil passage of a crankshaft, between a slide bush and a bearing to lubricate frictional surfaces thereof.
2. Description of the Related Art
Generally, a scroll compressor includes upper and lower scrolls respectively provided with involute-shaped wraps engaged with each other. One of the scrolls performs an orbiting motion with respect to the other scroll to reduce the volume of spaces defined between the scrolls, thereby compressing gas confined in the spaces.
As such a conventional compressor, a radial compliance scroll compressor is known. In such a radial compliance scroll compressor, an orbiting scroll thereof is backwardly moved when liquid refrigerant, oil or foreign matter is introduced into compression chambers defined between the orbiting scroll and the other scroll, that is, a fixed scroll, thereby abnormally increasing the gas pressure in the compression chambers. In accordance with the backward movement of the orbiting scroll, it is possible to prevent the wraps of the scrolls from being damaged due to the abnormally increased gas pressure.
FIG. 1 is a sectional view illustrating the entire configuration of a conventional radial compliance scroll compressor.
As shown in FIG. 1, the conventional radial compliance scroll compressor includes a shell 1, and main and sub frames 2 and 3 respectively arranged in the shell 1 at upper and lower portions of the shell 1. A stator 4, which has a hollow structure, is interposed between the main and sub frames 2 and 3 within the shell 1.
A rotor 5 is arranged inside the stator 4 such that it rotates when current flows through the stator 4. A vertical crankshaft 6 extends axially through a central portion of the rotor 5 while being fixed to the rotor 5 so that it is rotated along with the rotor 5. The crankshaft 6 has upper and lower ends protruded beyond the rotor 5, and rotatably fitted in the main and sub frames 2 and 3, respectively. Thus, the crankshaft 6 is rotatably supported by the main and sub frames 2 and 3.
An orbiting scroll 7 is mounted to an upper surface of the main frame 2 in the shell 1. The orbiting scroll 7 is coupled, at a lower portion thereof, with the upper end of the crankshaft 6, which is protruded through the main frame 2, so that it performs an orbiting motion in accordance with rotation of the crankshaft 6. The orbiting scroll 7 is provided, at an upper portion thereof, with an orbiting wrap 7a having an involute shape. The orbiting wrap 7a extends upwardly from an upper surface of the orbiting scroll 7. A fixed scroll 8 is arranged on the orbiting scroll 7 in the shell 1 while being fixed to the shell 1. The fixed scroll 8 is provided, at a lower portion thereof, with a fixed wrap 8a adapted to be engaged with the orbiting wrap 7a of the orbiting scroll 7 such that compression chambers 22 are defined between the wraps 7a and 8a. 
With this configuration, when the orbiting scroll 7 performs an orbiting motion in accordance with rotation of the crankshaft 6, gaseous refrigerant is introduced into the compression chambers 22 in a sequential fashion, so that it is compressed.
For the orbiting motion thereof, the orbiting scroll 7 is eccentrically coupled to the crankshaft 6. For this eccentric coupling, the crankshaft 6 is provided with a crank pin 10 upwardly protruded from the upper end of the crankshaft 6 at a position radially spaced apart from the center of the upper end of the crankshaft 6 by a certain distance. Also, the orbiting scroll 7 is provided, at the lower portion thereof, with a boss 7b centrally protruded from a lower surface of the orbiting scroll 7.
A bearing 11 is forcibly fitted in the boss 7b. Also, a slide bush 12 is slidably fitted around the crank pin 10. Thus, the crank pin 10 of the crankshaft 6 is rotatably received in the boss 7b of the orbiting scroll 7 via the bearing 11 and slide bush 12, so that the orbiting scroll 7 is eccentrically coupled to the crankshaft 6.
As a rotation preventing mechanism for the orbiting scroll 7, an Oldham ring 9 is arranged between the main frame 2 and the orbiting scroll 7. An oil passage 6a extends vertically throughout the crankshaft 6. Upper and lower balance weight members are provided at upper and lower surfaces of the rotor 5, respectively, in order to prevent a rotation unbalance of the crankshaft 6 caused by the crank pin 10.
In FIG. 1, reference numerals 15 and 16 designate suction and discharge pipes, respectively, reference numerals 17 and 18 designate a discharge port and a discharge chamber, respectively, reference numeral 19 designates a check valve, reference numeral 20 designates oil, and reference numeral 21 designates an oil propeller.
When current flows through the stator 4, the rotor 5 is rotated inside the stator 4, thereby causing the crankshaft 6 to rotate. In accordance with the rotation of the crankshaft 6, the orbiting scroll 7 coupled to the crank pin 10 of the crankshaft 6 performs an orbiting motion with an orbiting radius defined between the center of the crankshaft 6 and the center of the orbiting scroll 7.
In accordance with a continued orbiting motion of the orbiting scroll 7, the compression chambers 22, which are defined between the orbiting wrap 7a and the fixed wrap 8a, are gradually reduced in volume, so that gaseous refrigerant sucked into each compression chamber 22 via the suction pipe 15 is compressed to high pressure. The compressed high-pressure gaseous refrigerant is subsequently discharged into the discharge chamber 18 via the discharge port 17. The compressed high-pressure gaseous refrigerant is then outwardly discharged from the discharge chamber 18 via the discharge pipe 16.
FIG. 2 is an exploded perspective view illustrating the structure of the conventional slide bush.
As shown in FIG. 2, the slide bush 12 is fitted in the boss 7b of the orbiting scroll 7. The slide bush 12 is provided with a crank pin hole 12a so that it is fitted around the crank pin 10. In accordance with this arrangement, the slide bush 12 is radially shifted in a backward direction when an abnormal compression operation is carried out to cause an abnormal increase in the gas pressure of the compression chambers, thereby causing the orbiting scroll 7 to be radially shifted in the backward direction such that the orbiting wrap 7a is moved away from the fixed wrap 8a. An oil supply groove 12b is provided at an outer peripheral portion of the slide bush 12 at one side of the slide bush 12. The oil supply groove 12b may be formed by cutting out a desired peripheral portion of the slide bush 12.
FIGS. 3a to 3c illustrate a radial backward movement of the conventional slide bush. FIG. 3a is a cross-sectional view illustrating a state of the slide bush in a normal operation of the scroll compressor. FIG. 3b is a cross-sectional view illustrating a backwardly moved state of the slide bush caused by an abnormal operation of the scroll compressor. FIG. 3c is a sectional view illustrating supply of oil in the normal operation of the scroll compressor.
As shown in FIGS. 3a to 3c, in the normal operation of the scroll compressor, the crank pin 10 performs an orbiting motion along with the slide bush 12 in accordance with rotation of the crankshaft 6. When the gas pressure in the compression chambers is abnormally increased due to introduction of liquid refrigerant, oil or foreign matter into compression chambers during the normal operation of the scroll compressor, the slide bush 12 is radially shifted in a backward direction along the crank pin hole 12a with respect to the crank pin 10 in response to the increased gas pressure.
Meanwhile, oil 20 is supplied to the eccentric coupling device via the oil passage 6a formed through the crankshaft 6 during the normal operation of the scroll compressor. As the orbiting scroll 7 performs an orbiting motion, the oil 20 supplied to the eccentric coupling device is discharged from an upper end of the crank pin 10, so that it lubricates the bearing 11 and slide bush 12 fitted in the boss 7b of the orbiting scroll 7 while being in frictional contact with each other, thereby reducing friction generated between the bearing 11 and the slide bush 12. The oil 20 also serves to cool the stator 4 and rotor 5.
However, when the slide bush 12 is radially moved in the backward direction along the crank pin hole 12a due to an abnormal increase in the gas pressure of the compression chambers, the crank pin hole 12a is enlarged at one side of the slide bush 12, as shown in FIG. 3b. That is, the crank pin hole 12a has an enlarged gap at one side of the slide bush 12. As a result, the oil discharged from the upper end of the crank pin 10 via the oil passage 6a of the crankshaft 6 is mainly discharged through the enlarged gap of the crank pin hole 12a without being sufficiently supplied between the bearing 11 and the slide bush 12, that is, frictional surfaces thereof.
Due to such insufficient oil supply, a large frictional force is generated between the frictional surfaces, thereby causing the slide bush to be inclined at one side thereof. That is, a tilting phenomenon may occur.
Due to such a tilting phenomenon, the orbiting scroll cannot perform a smooth orbiting motion, thereby causing a degradation in the compression efficiency of the scroll compressor.
Furthermore, a large amount of frictional heat may be produced due to friction generated between the crank pin and the slide bush. The frictional heat may increase the temperature of the compression chambers, thereby causing a further degradation in the compression efficiency of the scroll compressor. The elements of the scroll compressor may also be damaged.